By paying attention to hand position and wrist angle as you complete the underwater portion of your stroke, you'll be able to access more speed and power.
The Drill: To begin, stand upright on a flat surface, feet about 4-6 inches apart. Drop your arms by your side and mentally mark where your thumbs naturally line up with each thigh. Once swimming freestyle, you want to lightly drag your thumb across this spot during the underwater pull-through. This will insure that your arm is extending behind you (refer to swimmer in figure 2). Very simply, this drill taps into your muscle memory. You want to get used to pulling all the way through extending the arm behind you.
For general propulsion and hand forearm technique
This Single Arm drill allows you to concentrate on stroke accuracy. By isolating one arm, it allows you to focus on improving technique.
Fist drill is near impossible to complete with a dropped elbow and for this reason alone is worth giving a shot. The focus is strong kick, long body and closed fists while feeling water pressure across the forearm. The drill can be completed with a tennis ball or add a snorkel, fins to embed the stroke pattern